snegov/cura-te-ipsum
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Make dry-run genuinely non-mutating (#23)

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* Make dry-run genuinely non-mutating

fs.rsync() now takes a real dry_run code path: every mutating call
(copy, delete, chmod, chown, utime) is skipped, and a missing dst_dir
is never created - the same comparison logic still runs so the yielded
actions match what a real run would do.

backup.initiate_backup() diffs each source directly against the latest
completed snapshot on dry-run, instead of building and discarding a
throwaway staging directory with real hardlinks. cleanup_old_backups()
no longer creates the repo-id file as a side effect of a dry-run.

cli.py skips lock acquisition entirely on dry-run (set_backups_lock()
writes PID/timestamp metadata, itself a mutation) and exposes the
retention policy via --keep-all/--keep-daily/--keep-weekly/
--keep-monthly/--keep-yearly.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

* Address Copilot review: guard restore lock release, reject negative retention values

- Guard restore --dry-run's finally block the same way backup's is
  guarded, for symmetry (release_backups_lock() was already a safe
  no-op when unheld, but this makes the dry-run contract explicit
  rather than relying on that implementation detail).
- Reject negative --keep-* values via a dedicated argparse type: a
  negative threshold shifts retention comparisons into the future and
  can make cleanup treat every existing backup as deletable.
- Add a restore --dry-run lock-skip regression test, mirroring the
  existing backup one.
- Fix _snapshot_all_stats() in the new dry-run non-mutation test to
  also record the backups_dir root's own stat, not just its children.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

---------

Co-authored-by: Maxim Shulga <maxim.shulga@alludo.com>
Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>
This commit is contained in:
snegovClaude Sonnet 5Maxim Shulga
 authored and GitHub committed 2026-08-09 01:39:53 +00:00
1 parent 699c569cc2
commit 22757ece58
8 files changed
+478 -51
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curateipsum/cli.py
+71 -6
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@@ -29,6 +29,20 @@ def _normalize_argv(argv):
return ["backup", *argv]
def _nonneg_int(value: str) -> int:
"""
argparse type for --keep-* options: a negative threshold shifts
retention comparisons into the future, which can make cleanup treat
every existing backup as eligible for deletion.
"""
parsed = int(value)
if parsed < 0:
raise argparse.ArgumentTypeError(
"must be zero or a positive integer, got %r" % value
)
return parsed
def _build_parser():
parser = argparse.ArgumentParser(
prog="cura-te-ipsum",
@@ -72,6 +86,40 @@ def _build_parser():
default=False,
help="Use cp command for creating hardlink "
"copies")
backup_parser.add_argument("--keep-all",
type=_nonneg_int,
default=7,
metavar="DAYS",
help="keep every backup up to this many days "
"in the past (default: %(default)s)")
backup_parser.add_argument("--keep-daily",
type=_nonneg_int,
default=30,
metavar="DAYS",
help="keep one backup per day up to this "
"many days in the past "
"(default: %(default)s)")
backup_parser.add_argument("--keep-weekly",
type=_nonneg_int,
default=52,
metavar="WEEKS",
help="keep one backup per week up to this "
"many weeks in the past "
"(default: %(default)s)")
backup_parser.add_argument("--keep-monthly",
type=_nonneg_int,
default=12,
metavar="MONTHS",
help="keep one backup per month up to this "
"many months in the past "
"(default: %(default)s)")
backup_parser.add_argument("--keep-yearly",
type=_nonneg_int,
default=5,
metavar="YEARS",
help="keep one backup per year up to this "
"many years in the past "
"(default: %(default)s)")
backup_parser.add_argument("sources",
nargs="+",
metavar="SOURCE",
@@ -143,7 +191,11 @@ def _run_backup(args) -> int:
start_time = time.time()
if not backup.set_backups_lock(backups_dir_abs, args.force):
# A dry-run never writes anything, including lock metadata, so it
# doesn't need to acquire the lock at all - only a real run has to
# serialize against other backups/restores.
if not args.dry_run and not backup.set_backups_lock(
backups_dir_abs, args.force):
return 1
exit_code = 0
@@ -160,13 +212,21 @@ def _run_backup(args) -> int:
external_rsync=args.external_rsync,
external_hardlink=args.external_hardlink,
)
backup.cleanup_old_backups(backups_dir=backups_dir_abs,
dry_run=args.dry_run)
backup.cleanup_old_backups(
backups_dir=backups_dir_abs,
dry_run=args.dry_run,
keep_all=args.keep_all,
keep_daily=args.keep_daily,
keep_weekly=args.keep_weekly,
keep_monthly=args.keep_monthly,
keep_yearly=args.keep_yearly,
)
except backup.BackupFailedError as err:
_lg.error("Backup failed: %s", err)
exit_code = 1
finally:
backup.release_backups_lock(backups_dir_abs)
if not args.dry_run:
backup.release_backups_lock(backups_dir_abs)
end_time = time.time()
spent_time = end_time - start_time
@@ -189,7 +249,11 @@ def _run_restore(args) -> int:
# while it's still in progress. set_backups_lock() already logs why
# (e.g. "Previous backup is still in progress") - add restore-specific
# context here so a restore failure doesn't read like a backup one.
if not backup.set_backups_lock(backups_dir_abs, args.force):
# A dry-run never writes to dest_dir, so it doesn't need this
# protection - nothing it reads can be invalidated by a concurrent
# writer in a way that produces anything worse than a stale preview.
if not args.dry_run and not backup.set_backups_lock(
backups_dir_abs, args.force):
_lg.error("Could not acquire the backups lock, restore aborted "
"(use --force to wait for it instead)")
return 1
@@ -243,7 +307,8 @@ def _run_restore(args) -> int:
else:
_lg.info("Verified: restored content matches the manifest")
finally:
backup.release_backups_lock(backups_dir_abs)
if not args.dry_run:
backup.release_backups_lock(backups_dir_abs)
return exit_code